The present invention relates to an exhaust gas purification device for an internal combustion engine.
Japanese Unexamined Patent Publication (Kokai) No. 6-159037 discloses an exhaust gas purification device, for a diesel engine, in which a filter for trapping particulates in the exhaust gas is arranged in the exhaust passage of the engine and both of the upstream and downstream side surfaces of the filter with respect to the exhaust gas flow are covered with a NOx storing member for storing the nitrogen oxide NOx temporarily. Generally, the exhaust gas of the diesel engine contains particulates, i.e. the soot (carbon) and soluble organic components (SOF), and NOx. Releasing these particulates into the atmosphere is not desirable. For this reason, the exhaust purification device traps the particulates in a filter and stores NOx in the accumulation member.
The NOx storing member covering the upstream side surface of the filter with respect to the exhaust gas flow, however, comes into contact with the exhaust gas containing the particulates. The problem, therefore, is that once the NOx storing member is poisoned by the particulates, it cannot satisfactorily store NOx any longer.
An object of the present invention is to provide an exhaust gas purification device capable of securing the NOx storage capacity of the NOx storing member.
According to the present invention, there is provided an exhaust gas purification device, for an internal combustion engine having an exhaust passage, comprising a filter arranged in the exhaust gas passage for trapping the particulates in the inflowing exhaust gas and a NOx storing member arranged only on the downstream side surface of the filter with respect to the exhaust gas for temporarily storing the NOx in the inflowing exhaust gas therein.